DIGESTION. 169 



in a neutral mixture ; and is nearly or quite suspended in the presence 

 of a dilute acid. Under favorable conditions it dissolves not only coag- 

 ulated fibrine and albumen, but also the substance of animal tissues. 

 In his experiments with the tissue of the pancreas, Ku'hne placed the 

 finely divided gland in warm water, with a weighed quantity of the 

 substance to be experimented on ; allowing the infusion of the pancreas 

 and the digestion of the albuminous matter to proceed simultaneously. 

 He found that when employing for this purpose a dog's pancreas of 

 from 50 to 60 grammes weight, 400 grammes of boiled and pressed 

 fibrine were reduced to an insignificant residue in from three to six 

 hours, the reaction of the mass continuing faintly alkaline. 



The action of the pancreatic ferment on albumenoid matters differs 

 from that of pepsine in its details, but is the same in its result. If 

 coagulated fibrine be immersed in pancreatic juice or an alkaline tryp- 

 sine solution, it doe.s not become swollen and gelatinized, nor is it 

 transformed into syntonine as it would be in gastric juice. The pieces 

 of fibrine become rather shrivelled and condensed, and are afterward 

 liquefied without passing through the modification of syntonine. But 

 when liquefaction is accomplished, the substance in solution has all the 

 characters of peptone, in the same degree as if produced by stomach 

 digestion its non-coagulability by heat, its solubility in water, in dilute 

 acids and alkalies, and in neutral solutions, and its diffusibility through 

 animal membranes. The final change produced by trypsine in albu- 

 menoid substances appears, therefore, to be a hydration, but effected by 

 a different process from that of digestion with gastric juice. 



It seems evident, accordingly, that the pancreas during life produces 

 a ferment which is capable of dissolving its own tissue. The difficulty 

 of accounting for such a fact is greater in this case than in that of the 

 stomach ; since the pancreatic ferment is most active in presence of an 

 alkaline reaction, like that of the blood and the interstitial fluids of the 

 tissues. It is indicated by the experiments of Haidenhain that trypsine 

 is not contained under its own form in the glandular cells during life, 

 but is produced, at the moment of secretion or after death, from a pre- 

 existing inactive substance, termed "zymogen." There are, no doubt, 

 such preliminary stages in the formation of all ferment bodies ; but the 

 trypsine ferment is actively present in freshly secreted pancreatic juice, 

 and its mode of production from the preceding inert material must be 

 for the most part a matter of surmise. The pancreas does not appear 

 liable, like the stomach, to self-digestion after death, though the sur- 

 rounding conditions would seem often favorable to such an alteration. 



The third substance of this kind in the pancreatic juice, causing 

 decomposition of the neutral fats, with liberation of a fatty acid, has 

 not received a distinct name. It is known, however, by its action 

 whenever fresh pancreatic juice, an infusion of the pancreas, or its 

 moist tissue, is brought in contact with liquid neutral fat at the temper- 

 ature of 35 to 40 C. In a short time an acid reaction becomes 

 manifest, sufficient to redden blue litmus-paper, and on keeping the 



